A procedure for preparation of hPRL isohormones B and C by isoelectric focusing was worked out. 2) Glucocorticoid receptor from the 2-week chick embryonic retina was physically characterized by PAGE. 3) A procedure for isolation of hGH isohormones D and E by electrofocusing was developed. The isolation procedure using preparative isotachophoresis was modified by electrophoretic extraction and concentration of the isohormones, but failed to provide homogeneous hGH-E and -D. 4) Insulin receptor was physically characterized by PAGE in Triton X-100. Characterization in other detergents expected to yield greater disaggregation without inactivation is in progress. 5) Tetanus toxin was physically characterized by PAGE and IFPA. Heterogeneity progressing as a function of time after radioiodination was demonstrated by IFPA. 6) Rationales for solubilization and disaggregation of membrane proteins based on micellar properties for separation by PAGE and IFPA were developed. 7) hCG CR119 standard was characterized by IFPA with regard to the constituent isohormones and their properties.